1. Field of the Invention
The invention concerns an apparatus which is suitable for permeating solid materials with various solutions and is particularly directed to processes for the demineralization of bone tissue. The invention is also directed to an apparatus for performing the processes.
2. Description of Background Information
It is known that implementation of acid demineralized bone (DB) in the form of a powder in extraskeletal sites stimulates new bone formation. Various research groups (Syftestad, 1982; Urist et al., 1967; Urist and Strates, 1970; Urist & Strates, 1971; Urist et al., 1983) have suggested that a noncollagenous protein present in demineralized bone has the ability to induce new bone formation when present within the implanted bone matrix.
Procedures presently utilized to demineralize ground bone fragments involve the use of ethanol to remove lipids and hydrochloric acid to remove the mineral component of bone.
It is also known to treat bones and bone particles to render them biocompatible so that they can be implanted in living animal and human bodies without being rejected. Included among the known methods for treating bone is the delipidization of bone using ethanol or chloroform. It is further known to demineralize bone matrix with an inorganic acid such as hydrochloric acid.
Demineralized, defatted bone can be further treated with antibacterial and antifungal agents to help prevent infection upon implantation into a living organism.
SEYEDIN et al., U.S. Pat. No. 4,434,094, describes the fragmentation of bone into small pieces and subsequent treatment by extraction with ethanol ethylacetate to remove lipids from the bone fragments. Calcium phosphate is next dissolved from the bone matrix by contacting the bone particles with dilute hydrochloric acid for one hour up to several days.
JEFFERIES, U.S. Pat. No. 4,394,370, discloses a similar method of demineralization wherein bones are first cleaned and extracted with absolute ethanol followed by anhydrous ethyl ether. The bones are then pulverized and sieved to a standard particle size. Demineralization is achieved through extraction with 0.5N hydrochloric acid for at least three hours followed by multiple washes in sterile distilled water to remove calcium and acid residues, followed by multiple sequential 60-minute washes in ethanol and anhydrous ether.
Although it is well known to defat and demineralize bone for implantation purposes, known methods of demineralizing and removing lipids have been extremely tedious, labor intensive and slow. Furthermore, an excessive amount of handling and/or exposure of the bone to non-sterile conditions has been necessary during the various phases of processing.
Delipidization and demineralization of bone matrix has been conducted largely through soaking the bone matrix in extraction solutions. Demineralization of bone involves the solubilization of hydroxyapatitic materials using fairly strong acids. As demineralization proceeds, the solubilized hydroxyapatitic materials act to buffer the acidic solution thereby raising the pH. This renders the acid less effective, and demineralization thus takes longer, or greater volumes of acid are required, because the acid solution must be completely changed to restore the pH to an effective level.